Invasive Thoughts about a Previous Love Interest

Hope this is the right community to address this but NEED to communicate this without judgement. Keep in mind I’m in my early 20s and the guy I can stop thinking about is from my teen years. I have no intention on reaching out or starting a relationship with this guy but I can’t help but keep thinking about him recently. Mind you, I’m having a bit of difficulties in my current relationship due to his family and long distance…but I am in love with my current partner. Bc of the distance we agreed to be open and though it’s new, it seems to let off a lot of stress.

BUT I DIGRESS. I haven’t really said more than a full convo to This guy from high school and yet I think about sleeping with him constantly. I don’t know if it’s bc of all the severe stressors in my life, if it’s real feelings, or lust, but I know that he has been plaguing my head and making me think crazy *** like that’ll make me look like a delusional train-wreck like dming him on ***. I even find myself slightly jealous? about girls he might’ve been with though I’ve had other partners in my life and also satisfied emotionally with my current relationship. Anybody else dealt with this? He was a love interest from junior high and I don’t think he is that nice (but can you say you know someone if it’s been 10 years since you last spoke?). I’m rambling but it’s been in my head for the past 2 weeks and I guiltily enjoy the fantasies but I know it isn’t good either. help!